Formula and calculator of the member of an arithmetic progression

How to find a₁ in arithmetic progression on the Prostobank.com calculator?

With our calculator you can find the value of any member of the progression, including the first (a₁). To do this, you need to write the value of the known member of the progression (the index of the first member cannot be less than 1), the step and the number of the sought member of the progression. If you need to find the first member of a progression, write the number 1 in the window with the number of the member of the progression you are looking for. After these simple steps, you will instantly know the value of the first or n-th term of an arithmetic progression.

Formula of a member of an arithmetic progression

a_n = a₁ + (n – 1) × d, a₁ – the first member of the progression, n is the number of members of the progression, d is the step of the progression

Formula for the first term of an arithmetic progression

a₁ = a_n – (n – 1) × d